Getting a Charge Out of Manure and Seawater
DEBBIE ELLIOTT, host:
It's time now for another episode of Science Out of the Box here on ALL THINGS CONSIDERED. And this week, NPR science correspondent Richard Harris is here in the studio with me and he has actually brought a box.
RICHARD HARRIS: Indeed, I have. Yes. I wanted to talk to you a little bit about electricity and unusual ways of generating electricity. So let me open this box. And inside I have...
ELLIOTT: A potato.
HARRIS: A potato. And a few other odds and ends that will come in useful.
ELLIOTT: Some green and red wires.
HARRIS: And here is a...
ELLIOTT: A nail.
HARRIS: A nail covered with zinc. So now I'm going to stick that nail into the potato. I'm going to stick the copper wire into the potato as well.
HARRIS: Here you go. And we can now actually use this potato to generate electricity. Actually, the potato is only providing some liquid for the electricity to run through. What's going to happen is charged particles from the zinc on the nail want to float to the copper, if you give them an opportunity to do so.
ELLIOTT: Why do they want to do that?
HARRIS: It's just - it's one of those facts of nature. It's called electro-chemistry. But basically there's a potential between the two of them and if give them a chance, they will.
ELLIOTT: Put them in a potato, that's what they're going to do.
HARRIS: Yeah, or even a glass of salty water would work as well, but the potato is just - it's decorative and it's an easy way to hold things together. So at any rate, I'm going to take a little wire and clip it on the nail on one end, and I'll take the other end of the wire and I'm going to clip it onto the copper wire that's going into the potato. And if you'd like to hold this tiny little meter, you can tell me what happens when I clip on the meter.
ELLIOTT: The little red indicator moved.
HARRIS: Yup, a tiny, tiny amount of juice is coming out of this, both - actually potato juice as well as electricity coming out of this. What you're seeing is the flow of electrons that start at the nail and flow to the wire and then around through the meter to show - and that meter tells you that there's electricity flowing.
So but this is a tiny, tiny amount of electricity, just barely enough to make the needle on that meter wiggle a little bit, not really enough to do anybody any good at all.
But a couple weeks ago, I was up at Harvard University and I met a biologist who's experimenting with something that's almost as simple but it produces 10,000 times more energy.
HARRIS: Yeah. His name is Peter Gurgis(ph) and he took me into his lab.
(Soundbite of lab)
HARRIS: Peter Gurgis actually studies bacteria that live in the mud at the bottom of the ocean. And it turns out these bacteria can be tricked into generating electricity. This isn't just cool science, it's potentially cool technology. He takes me into a windowless room in the back of his lab and he proudly displays a clear plastic container with some brown goop at the bottom.
Mr. PETER GURGIS (Harvard University): Believe it or not, this is one microbial fuel cell.
HARRIS: You just cut the top off of a water cooler basically.
Mr. GURGIS: Yup.
HARRIS: He peers inside -
Mr. GURGIS: And down here, this is cow manure. I mean, so it's literally livestock waste. And I put a layer of sand to kind of keep them separated and then this, the top here is filled with sea water.
HARRIS: Do you have a name for this gizmo?
Mr. GURGIS: Yeah, this is our bucket light.
HARRIS: The electricity here comes from bacteria that are in the manure under the layer of sand. As they eat the manure, they produce electrons. They have to get rid of them - and we also get rid of electrons when we eat by splitting oxygen atoms and breathing out carbon dioxide. Well, these bacteria don't have a handy place to dump their electrons. There's no oxygen in the muck.
So here's the trick. Peter Gurgis gives them a place to dump their electrons, essentially wires that run through the mud. Voila. An electric current.
He got interested in this because he was interested in understanding the bacteria, but now he wants to take this basic science out of the box and apply it to a very different real world problem.
Mr. GURGIS: There's about two and a half or three billion people living worldwide in areas away from distributed electricity. And most of them use livestock manure or they'll burn food scraps in their homes to produce light. And as a consequence they suffer; in particular women and children have high rates of emphysema and lung cancer because of this. So what if we could use this to generate light? And that's a project that we're really excited about and we're currently raising funds for.
HARRIS: So how much light does the light bulb put off?
Mr. GURGIS: This five-gallon bucket design produces enough electricity to power an LED for most of the evening hours.
HARRIS: An LED is a light-emitting diode. These super-efficient lights are used in newfangled laptop screens; they're in camping headlights and what have you. Peter Gurgis's bucket of muck makes just a tiny trickle of electricity, but it does it 24 hours a day for months and months on end, so he collects that electricity and stores it in a device called a capacitor. He hopes e-groups will buy the electronic part of this bucket light and make them available cheaply all around the world.
Mr. GURGIS: It's probably going to cost a couple of dollars to fabricate these LED capacitor units. And you could imagine producing, you know, millions upon millions of these little cells, and that's what person would go to the store to buy. And I'm certain that people are going to get really innovative and clever with this. I mean, why not scale it up? I mean, I could have 12 of these. Or what if I wanted to set this up in my outhouse? Seriously. There's no reason this wouldn't work in your outhouse.
And what's really cool is we're just developing these small circuit boards that allow us to charge cell phones.
HARRIS: Light and communications. Ways to a better life. Now, Peter Gurgis isn't the only one out there trying to use bacteria to generate electricity. Seventy-five miles to the west of the Gurgis lab, you will find Derek Lovely at the University of Massachusetts in Amherst. He's a leading light in the field, if you'll pardon the expression.
Mr. DEREK LOVELY (University of Massachusetts): It's been known basically since 1910 that microbes can produce electricity. It's just been within the last four or five years, though, that we've understood kind of a new microbial process which is much more efficient and effective in producing electricity over the long term.
HARRIS: Lovely started his research with funding from the Pentagon to produce power in the mud at the bottom of the ocean for various electronic sensors. But his interests are also much broader.
Mr. LOVELY: We're actually funded even to develop fuel cells in the long term for powering vehicles.
HARRIS: That's not going to happen anytime soon, considering how much energy cars gulp, but Lovely does use these fuel cells to power toy cars. And my potato here certainly couldn't do that.
ELLIOTT: So it's a way to basically turn waste into energy at some level.
HARRIS: Absolutely. A nice and clean way to do it.
ELLIOTT: NPR's Richard Harris. Thanks so much.
Mr. HARRIS: My pleasure.